Shao-Hua Fang

Abundant Triassic spinicaudatans from China have been commonly assigned to the genus Euestheria Depéret & Mazeran. However, recent SEM-based studies have revealed that many of them do not belong to euestherids, as evidenced by their distinctive micro-ornamentations, revealed by scanning electron microscopy (SEM). In this study, we describe two spinicaudatan species, Polygrapta yipinglangensis comb. nov. and P. dazuensis comb. nov., which were previously identified as members of Euestheria from the Upper Triassic Ganhaizi and Xujiahe formations in south-western China. The carapace ornamentations of these species exhibit fine polygonal reticulations in the upper parts, which gradually transform to linear arrangements and radial lirae at the ventral regions. Based on these features, they are classified into Polygrapta Novojilov. Although the two species exhibit morphological similarities, they can be distinguished by variations in reticulation size and the width of linear arrangements in their marginal areas.

Clam shrimps are one of the most common and representative invertebrates in continental strata and are endowed with important biostratigraphic and paleoecological values. The genus Euestheria is one of the most common clam shrimp taxa that has been recorded in the latest Paleozoic and the Mesozoic around the world. A list of all the species assigned to Euestheria, recorded from the Devonian to the Cretaceous across all seven continents as of September 2024, is provided. The list may serve as a valuable resource, potentially useful for the biostratigraphic division and long-range correlations of continental strata. In addition, the taxonomic issues of the genus are briefly introduced and examined herein. The study aims to provide a simple lead-in for all the researchers who have an interest in clam shrimp and the genus Euestheria.

A new spinicaudatan species Triglypta jiyuanensis Liao & Huang sp. nov. is described from the Upper Jurassic Maao Formation in the Jiyuan Basin, northwestern Henan Province, China. The carapace of the new species is ornamented with punctae, linear arrangements of punctae, and radial lirae. The new species differs from those of the early Triglypta forms from the Middle Jurassic but closely resembles T. jianchangensis Wang, 2014 from the Upper Jurassic Tiaojishan Formation of western Liaoning Province. Our study provides new biostratigraphic evidence supporting that the Maao and Tiaojishan formations can be correlated. Moreover, we suggest that the Yangshuzhuang Formation in the Jiyuan Basin could correlate to the Haifanggou and the Longmen formations in the Yanliao area.